Patent GB-748225-A (GB)
Title: Improvements in or relating to gas-blast electric circuit-breakers
Inventor: WILD ROBERT WILLIAM
IPC: H01H33/867
Filed: 1953-04-07
Abstract: 748,225. Gas-blast switches; switch contacts; actuation of switches. REYROLLE & CO., Ltd., A. July 7, 1954 [April 7, 1953], No. 9387/53. Class 38(5) [Also in Group XXIX] In a circuit breaker suitable for the higher voltage range, the nozzle through which an arc extends between contacts respectively on the upstream and downstream side thereof and which, at arcinitiation is spaced from the upstream one, is arranged to move further away therefrom after a given time after arcinitiation and in the direction of the blast. The nozzle may be metallic and either connected to or insulated from the downstream contact, or insulating. The upstream contact D comprising spring fingers D<SP>2</SP>, a spring plunger D<SP>3</SP>, and hemispherical stress shield D<SP>4</SP>, is mounted on a condenser-type bushing D' in a metal container containing high-pressure gas. An impedance G arranged as in Specification 743,787 is connected to a hemispherical probe electrode G' acting as a stress shield, a further stress shield H separating the container A from the exhaust chamber C containing the downstream contact E which houses the pneumatically-actuated movable arc-initiating contact F. The pressure-gas container is normally cut off from atmosphere by a diaphragm-type valve arranged as in Specification 736,088. The annular flexible diaphragm K<SP>1</SP> is clamped between metal plates J, J<SP>1</SP> having co-operating projections at intervals round their periphery to provide exhaust ports. The valve member K is normally urged by springs H<SP>2</SP> so that annular valve elements K<SP>2</SP>, K<SP>3</SP> thereon seat upon flexible seatings J<SP>5</SP>, J<SP>6</SP> on tne plates J, J<SP>1</SP>, the member K being moved to open position by means of two concentric cylindrical flanges K<SP>4</SP>, K<SP>5</SP> the ends of which act as cams by engaging rollers L<SP>1</SP>, L<SP>2</SP> arranged at diametrically-opposed points of a rotary, pneumatically-actuated member L. The cams are relatively displaced by 180 degrees and the arrangement is such that rotation of member L through 300 degrees in either direction will quickly open valve K shortly after the start of the stroke and permit its reclosure shortly before the end of the stroke. The member L carries a further pair of rollers L<SP>3</SP>, L<SP>4</SP> which co-operate with similar cams B<SP>1</SP>, B<SP>2</SP> on the nozzle B'which is guided on pins B<SP>4</SP> and returned by springs B<SP>5</SP>. The timing is such that, in opening, the nozzle B is projected to engage the probe electrode G<SP>4</SP>, the valve K is opened, the contact F is withdrawn from the contact D to draw an arc and transfer it to contact E, and the nozzle is retracted after a time sufficient to allow extinction of the arc. The secondary arc drawn between the nozzle Band electrode G<SP>4</SP> in series with impedance G is also blown out by the residual blast before the valve K finally closes, the nozzle then co-operating with contact E to secure gas-tightness of the container if the valve should fail to seal. The member L is carried on a rotor L<SP>5</SP> carrying a vane L<SP>6</SP>, Fig. 2, movable in an arcuate cylinder through 300 degrees in either direction to effect an opening operation, control' being effected by valves M<SP>3</SP>, M<SP>4</SP> each having a bleed hole and functioning alternatively as inlet and exhaust (cushioning) valve and in timed relationship to the air supply to contact F. The Specification refers also to automatic reclosure (the nozzle B being projected to engage electrode G<SP>4</SP> and final opening of the circuit at a series isolator, to modifications wherein no impedance is employed, and to an arrangement wherein a pneumatically-actuated contact engages the upstream contact laterally, the blast is produced by admitting air to the container via an inlet valve, and the nozle is latched in projected position and released by the gas-pressure (Fig. 3, not shown). According to the Provisional Specification, the movable contact may be spring closed or may be opened in a direction opposite to the blast gas.